Currently, air flow meters, provided in an electronic controlled fuel injection apparatus of an internal combustion engine such as an automobile to measure an intake air amount have been used. Further, thermal fluid flow sensors using a heating resistor have attracted attention as a fluid flow sensor used in such the air flow meter in terms that it is possible to directly detect a mass air flow.
Among them, a thermal air flow sensor, that is, an air flow sensor, which is manufactured by a micro electro mechanical systems (MEMS) technique using a semiconductor, can reduce the manufacturing cost and be driven, which has attracted attention.
As such a thermal fluid flow sensor, there is a sensor which includes a heating resistor and in which a flow detection section to detect a flow rate of a fluid and a circuit section to perform to perform control of the flow detection section or the like are formed on the same substrate. In this case, it is unnecessary to electrically connect the flow detecting substrate and the circuit substrate using a method such as wire bonding, which can reduce the number of parts.
PTL 1 (JP 2004-518119 A) discloses a micromechanical flow sensor in which a measuring element and a circuit are integrated in a semiconductor substrate, and the measuring element is provided on an opening of the semiconductor substrate or a recess.
PTL 2 (JP 2012-202786 A) discloses a thermal fluid flow sensor that includes a detection part, which includes a heating resistor provided on a first stacked film on a semiconductor substrate, and a circuit part which is provided on the semiconductor substrate and includes a control circuit and to control the heating resistor.